The invention relates to a high-pressure cleaner with a reciprocating pump, on which there is positioned a pump head into which at least one piston, which can be moved back and forth in the longitudinal direction of the reciprocating pump, projects, the pump head comprising a suction connection, for feeding a cleaning liquid, and a pressure connection, for discharging the cleaning liquid, and accommodating a plurality of regulating valves, and the pump head being produced from plastics and being braced with the reciprocating pump by means of a clamping element, the clamping element having at least one U-shaped clamping bracket with a base part butting against the pump head and with two legs aligned substantially in the longitudinal direction of the reciprocating pump.
Reciprocating pumps, which can be used, for example, in high-pressure cleaners, are described in U.S. Pat. No. 5,215,443 A and DE 42 09 461 A. The reciprocating pumps each have a pump head, it being proposed in DE 42 09 461 A to use a pump head made of plastics if the pump is used for low pressures.
A high-pressure cleaner having the features specified in the introduction is known from DE 195 48 498 C2. This document proposes to produce the pump head from plastics, so that it can be produced cost-effectively and has a relatively low weight. In order for it to be possible to withstand high pressures occurring during operation of the high-pressure cleaner and the considerable mechanical loading associated therewith, the abovementioned patent specification proposes a clamping element with the aid of which the pump head can be braced with the reciprocating pump. The clamping element is formed here as a cap which is configured in the manner of a framework and has a multiplicity of cross-pieces, which extend obliquely in relation to the longitudinal axis of the reciprocating pump, and a connection pipe into which the pressure connection, formed as a pressure stub, of the pump head penetrates. Moreover, the clamping element comprises a supporting flange which butts against a step of the pressure stub and from which the cross-pieces extend in the direction of the reciprocating pump, obliquely in relation to the longitudinal axis of the reciprocating pump. The clamping element has, inter alia, a U-shaped clamping bracket with a base part butting against the pump head and with two legs aligned substantially in the longitudinal direction of the reciprocating pump. During the assembly of the high-pressure cleaner, it has to be ensured that the supporting flange of the clamping element butts against the corresponding step of the pressure stub of the pump head over the entire surface area.
DE 297 01 555 U proposes to connect a clamping element, as has been described in the abovementioned DE 195 48 498 C2, to the reciprocating pump by means of a connecting element which forms a positive fit both with the pump head and with the reciprocating pump. The use of such a connecting element, however, is associated with not inconsiderable production and assembly costs.
It is an object of the present invention to develop a high-pressure cleaner of the generic type such that it can be assembled more straightforwardly and allows a reliable connection between the pump head and reciprocating pump.
This object is achieved according to the invention, in the case of the high-pressure cleaner of the type described in the introduction, in that the free ends of the legs butt against an abutment surface, produced from metal, of a piston guide of the reciprocating pump and can be connected releasably to the reciprocating pump.
It has been found that the clamping-element design known from DE 195 48 498 C2 can be simplified to a considerable extent. All that is required in order to ensure satisfactory functioning of the pump head, produced from plastics, is for the clamping element to have at least one U-shaped clamping bracket, although it has to be ensured that the free ends of the clamping bracket butt against an metallic abutment surface of the piston guide of the reciprocating pump and are connected releasably, for example screwed, to the reciprocating pump. The clamping bracket ensures that the pump head, produced from plastics, can withstand even high pressures. For this purpose, the U-shaped clamping bracket engages around the pump head and butts directly against an abutment surface produced from metal. On account of the metallic configuration, the tightening torque to which the clamping bracket is subjected as it is fitted is maintained even during continuous operation of the high-pressure cleaner, loosening of the clamping bracket being avoided. Such loosening occurs, in particular, when the free ends of the legs of the clamping bracket butt against a plastics part since, on account of the high mechanical loading to which the plastics part is subjected by the clamping bracket, this plastics part plastifies over time, that is to say, in the case of an abutment surface produced from plastics, shrinkage takes place and results in loosening of the clamping element and thus in the functioning of the pump head, produced from plastics, being impaired. According to the invention, the abutment surface of the clamping element is thus produced from metal, so that the clamping element is prevented from loosening during the operation of the high-pressure cleaner. This, in turn, makes it possible for the clamping element to be configured with a particularly straightforward design.
The assembly of the high-pressure cleaner may additionally be simplified in that the piston guide of the reciprocating pump has through-passage openings which have connecting elements passing through them for the releasable connection of the clamping bracket to the reciprocating pump.
The reciprocating pump preferably comprises a cup-like pump housing on which the piston guide is positioned, and the clamping bracket can preferably be connected releasably to the pump housing.
Starting from the base part, which butts against the region of that end surface of the pump head which is directed away from the reciprocating pump, the legs of the clamping bracket can extend laterally in the longitudinal direction of the reciprocating pump, along the pump head, to approximately level with the pump housing.
It may alternatively be provided that the piston guide has metallic guide sleeves which are aligned in the longitudinal direction of the reciprocating pump, are directed towards the pump head and against the free ends of which the legs of the clamping bracket butt. The free ends of the guide sleeves thus form a metallic abutment surface for the clamping bracket and, since the guide sleeves are directed towards the pump head, it is possible for the length of the legs of the clamping bracket to be reduced, as a result of which a particularly stable design of the clamping element is achieved.
It is preferably provided that the connecting elements for the releasable connection of the clamping bracket to the reciprocating pump are formed as clamping screws which pass through the guide sleeves and are in engagement with a corresponding internal thread of the pump housing. The clamping bracket can be screwed to the pump housing by means of the clamping screws. In this case, the clamping screws pass through the guide sleeves of the piston guide, that is to say the connection of the clamping bracket to the pump housing simultaneously achieves mechanical securing for the piston guide.
In a design of the high-pressure cleaner which withstands particularly high mechanical loading, it is provided that the clamping screws are in engagement with an internal thread of the guide sleeves, so that the clamping element can be connected releasably to the piston guide of the reciprocating pump. Additional connecting elements are then provided for securing the piston guide mechanically on the pump housing of the reciprocating pump.
In a preferred embodiment, the clamping element has two U-shaped clamping brackets, a first clamping bracket engaging around the pump head in its lower region, adjacent to the suction connection, while the second clamping bracket engages around the pump head in its upper region, directed away from the suction connection. The use of two clamping brackets in a substantially mirror-symmetrical manner in relation to a centre plane aligned level with the pressure connection in the longitudinal direction of the reciprocating pump allows particularly uniform mechanical loading of the pump head. Tilting moments may thus be reliably prevented.
The two clamping brackets are preferably connected rigidly to one another via a connecting part since, as a result, the clamping element attains particularly high mechanical stability.
It is advantageous if the connecting element encloses the pressure connection of the pump head in the form of a ring since this simplifies the positioning of the clamping element during the assembly of the high-pressure cleaner. All that is necessary for this purpose is to position the clamping element with its connecting part on the pressure connection.
The clamping element butts against the free end surface of the pump head by way of the base parts of the two clamping brackets and, on account of the connection of the clamping element to the reciprocating pump, the pump head is subjected to a clamping force by the base parts. In an advantageous embodiment, it is provided that the connecting part has two lugs which project laterally, transversely to the longitudinal direction of the reciprocating pump, and butt against the pump head. The surface over which the clamping element butts against the pump head is increased in that this results in more uniform loading of the pump head and thus in increased mechanical stability.
It is advantageous if the clamping element is formed in one piece. This not only makes it possible to reduce the production costs, but also results in a mechanically more stable design.
The clamping element is preferably configured from metal, for example in the form of a sheet-metal part. It may alternatively be provided that the clamping element is formed as a diecasting, for example as a zinc or aluminium casting.